Photonic realization of chiral hinge states in a Chern-insulator stack

TL;DR

This paper demonstrates a photonic system that realizes and verifies chiral hinge states in a higher-order topological insulator, showcasing their robustness and potential for novel photonic applications.

Contribution

It introduces a simple method to construct chiral hinge modes using a Chern-insulator stack and verifies their existence and robustness experimentally in a photonic crystal.

Findings

Successful realization of chiral hinge states in a photonic crystal.

Experimental verification aligns with simulations.

Hinge states are robust against defects.

Abstract

Higher-order topological insulators, as a novel family of topological phases, are a hot frontier in condensed matter physics due to their adherence to unconventional bulk-boundary correspondence. A three-dimensional second-order topological insulator can support one-dimensional modes along its hinges (dubbed as hinge states). Here, we present a simple and direct method to construct chiral hinge modes based on a Chern-insulator stack. We analyze the existence of the hinge modes through the nontrivial quadrupole indices, and then design a photonic crystal to realize the specific flowing pattern of the hinge mode in our model. The experimental results align well with full-wave simulations, clearly demonstrating the existence of chiral hinge states. We also verify the robustness of these hinge states against defects in our photonic system.